The invention is directed to a process for the production of high temperature resistant, high density ceramic molded articles made of one or more components by the action of force on blanks at a temperature above 1300.degree. C. and at high pressure in a mold.
High temperature resistant ceramic molded articles are distinguished by a number of advantages; especially thereby the mechanical behavior above 1200.degree. C. plays an important role. As work materials, there are employed, for example, high temperature resistant oxides, carbides, nitrides, silicides borides, and mixtures of these materials.
The processes previously tired on an industrial scale for the production of such molded articles chiefly depend on molding of powders or mixtures of powders and subsequently sintering the blanks (molding-sintering-process). Furthermore, there are known processes for working up untreated or presintered ceramic molded articles by hot isostatic presses (HIP) (e.g., Am. Ceram. Soc. Bull. 54 (1975), Vol. 2, pages 201-205).
Since, because of the materials employed, the operating temperature both in the sintering and in the hot pressing are limited to below 2000.degree. C. the necessary high pressures, especially with high melting ceramics, are customarily obtained only by the addition of sintering adjuvants.
However, in a disadvantageous manner these can impart undesired creep properties with the high temperature behavior. A substantial disadvantage also is in the duration of the sintering process (several hours).
With hot isostatic presses, additionally the heat and pressure act simultaneously on the blank and the mold over a long time. This requires extremely expensive constructions, especially for thermal insulation of the hot construction components. The molding cycle as such likewise lasts for a long time and is customarily in the range of hours.
Therefore, it was the problem of the present invention to develop a process for the production of high temperature resistant, high density ceramic molded articles out of one or more components by the action of force on blanks at temperatures above 1300.degree. C. and high pressure in a mold, which process is carried out very rapidly without excessive demands on the mold and without the use of sintering adjuvants.